IR beams across waterway identify passing ships - by comparing hull and superstructure signatures with stored data from which irrelevant detail is suppressed

摘要

Ships moving along a waterway interrupt a pattern of IR light beams. Two beams, spaced along the waterway and close to water level, are interrupted by the hull. Their outputs are used for computing speed, direction and overall length. Two pairs of beams, at different heights in a vertical plane, are interrupted by the superstructure. Their outputs are processed to suppress irrelevant detail and converted to two frequency/length signature codes which represent superstructure outline, by combining beam outputs with speed and length data. The ship is identified by comparing length and the two signatures with stored data for all known ships, and selecting the one which gives the best fit. More than one set of data may be stored for each ship, to allow for tides and loading of the ship.